Your brass jewellery should last you a lifetime but it will tarnish over time through oxidisation. The best way to clean brass jewellery is with a mild natural acid like lemon juice or tomato ketchup (yes really!) and a soft cloth.
For a deeper clean, Brasso is a good product and safe to use for most people but if you have any skin allergies you should check the contents first. To restore the shine similar to its original professional polish some people use a clear enamel spray such as rust-oleum crystal clear enamel gloss. Here is a good article showing different methods to clean brass jewellery.
Ageing your brass jewellery
Some people prefer the aged look of brass instead of its shiny new look and want to achieve it right away. Well, that is also quite easy to achieve using just vinegar and salt. Here is a useful article with great tips on ageing your brass jewellery.
Protecting stones when cleaning brass jewellery
To prevent damaging any stones set in your brass jewellery during cleaning or ageing, cover the stone with a petroleum jelly such as Vaseline.
Preventing marks on the skin when wearing brass jewellery
Brass will sometimes leave green or grey marks on the skin if worn for a period of time, particularly if your skin is moist through heat or dampness in the air. Don’t let this put you off wearing brass jewellery because there are plenty of remedies on the internet for preventing brass marks on the skin.
The most popular and simple method is to use clear nail polish (not top coat nail polish) to cover the area of the jewellery that makes contact with your skin. However, other people suggest that by coating the jewellery you lose out on the therapeutic properties associated with wearing copper and zinc, which include pain relief and improved blood circulation. Any marks made on your skin wash off easily.